Plasma Expression Levels of Circulating miR-21 are not Useful for Diagnosing and Monitoring Colorectal Cancer.

Background: Recent evidence suggests that microRNAs play an important role in cancer diagnostics. We assessed plasma microRNA-21 levels in patients with colorectal cancer (CRC) at different stages and in patients with benign polyps. Methods: Plasma levels of miR-21 were assessed by quantitative reverse transcription polymerase chain reaction assay in plasma samples of 76 CRC patients and in 20 patients with benign polyps. Differences between groups were evaluated with Mann-Whitney and Kruskal-Wallis tests. Results: No significant differences of miR-21 plasma levels were observed between CRC patients and subjects with benign polyps (p > 0.05). Also, no significant differences were found between CRC patients with advanced (III-IV) or early cancer stages (I-II) (p > 0.05). Conclusions: These results do not support the hypothesis that circulating miR-21 expression is increased in adenoma-carcinoma-advanced carcinoma sequence. Accordingly, plasma miR-21 assessment does not appear to be a useful biomarker for diagnosing and staging CRC.